The present description relates to control of a spark ignited internal combustion engine having a fuel injector which directly injects fuel into the combustion chamber. It relates more specifically to a resumption of the fuel injection after a fuel shutoff.
It is known and described, for example, in Japanese Patent Application Publication No. 2002-332894 that the fuel injection is shutoff during a vehicle deceleration. The fuel injection is shutoff when the engine speed is a predetermined speed or greater and a desired torque for the engine is a predetermined torque or less that can be detected by detecting that a depression of the accelerator pedal is less than a predetermined value. When the engine speed reaches a predetermined fuel resumption speed during the fuel shutoff, or when the accelerator pedal depression reaches the predetermined value during the fuel shutoff, the fuel injection is resumed.
For decades, gasoline has been almost exclusively used for spark ignited internal combustion engines. In recent years, ethanol is becoming a more popular fuel to be used for spark ignited internal combustion engine as described, for example, in Japanese Patent Application Publication No. 2008-031948. While pure ethanol including one consisting of 97% ethanol and 3% water may be used as fuel, ethanol is usually mixed with gasoline to make fuel such as E10 (10% ethanol and 90% gasoline), E25 and E85.
When the fuel injection is resumed, an in-cylinder temperature is decreased because the combustion has been suspended so that the injected fuel may not evaporate or be atomized well in the combustion chamber. This is especially true when the fuel contains more ethanol since ethanol is less volatile than gasoline. Then, the combustion in the fuel resumption may be instable leading to deterioration of the drivability of the engine.
Therefore, there is room to improve the method to resume the fuel injection to a spark ignited combustion engine.